I'm new on this group, found it by scanning the netz for useful information for my HP41 emulation project.See https://sourceforge.net/projects/hp41cx for more information about this.Now I got a problem during implementation of the Time-Modul. I forked the phineas modul and wrote me own implementations to fit on the design.And after I tiped in XEQ 'CLOCK' ENTER the calculator runs in an undocumented?? opcode on the Timer-Module-Code.

As you can see on the log the programm writes the SCRegister and after LDI 192 it runs on 0x18 opcode which is not described anywhere.

Any idea?

Another problem is.If I ignore such undocumented opcodes (NOP), the calculator tries access to the periphery and ram in parallel. (Valid RAM and periphery (clock) selected)Is there any way to figure out which device (periphery or ram) shall be used?Any hint will be graceful.

As discussed in the Memory Organization chapter, there are unimplemented areas in theregister map in 41C mode. Accessing an unimplemented register causes the data_bus toremain floating, allowing an external device to drive the data_bus.

But who is the winner on this C=REGn statement. On my code it depends on the order of statement 1. and 2.

On the real hardware it must exist a mechanism which makes this behavior deterministics.But I don't know about. Maybe the device deselecting itself after specific activities? Maybe one of the opcode deselecting a previously selection of an devices or memory selection? Whatever I don't know. So any hint or information would be great to catch.